Permanent magnet device

ABSTRACT

A magnet arrangement for creating a magnetic field. The magnet arrangement includes a first magnet having a first surface defining a first pole and a second surface defining a second pole opposite the first pole, and a second magnet having a third surface defining a third pole and a fourth surface defining a fourth pole opposite the third pole. The second surface has a higher magnetic flux density than the first surface. The third surface has a higher magnetic flux density than the fourth surface. The second magnet is spaced from the first magnet to define a first gap between the second surface and the third surface. Magnetic field lines of the magnetic field run from the first surface to the second surface, from the second surface to the third surface through the first gap, and from the third surface to the fourth surface.

RELATED APPLICATION DATA

This application claims benefit under 35 U.S.C. Section 119(e) ofco-pending U.S. Provisional Application No. 60/997,687 filed Oct. 4,2007, which is fully incorporated herein by reference.

BACKGROUND

The present invention relates to a magnet assembly, and moreparticularly to a permanent magnet assembly for creating a periodicchange in magnetic field. The permanent magnet assembly could be used,for example, in a magnetic refrigeration device.

Magnetic refrigeration devices generally include magnets andmagnetocaloric material. The magnets are typically moved in analternating fashion relative to the magnetocaloric material such thatthe magnetocaloric material experiences an increasing magnetic fieldwhen the magnets move closer, heating up the magnetocaloric material,and a decreasing magnetic field when the magnets move farther away,cooling the magnetocaloric material. Typically, a heat transfer fluid ispassed through the magnetocaloric material to absorb the heat from themagnetocaloric material when the magnetic field increases, and the heattransfer fluid is then directed to a heat exchanger that releases theheat to the atmosphere. Then, the heat transfer fluid is passed throughthe magnetocaloric material to give up heat to the magnetocaloricmaterial when the magnetic field decreases and the heat transfer fluidis directed to another heat exchanger to remove heat from air beingcirculated into a cooled space.

SUMMARY

In one aspect, the invention provides a magnet arrangement for creatinga magnetic field. The magnet arrangement includes a first magnet havinga first surface defining a first pole and a second surface defining asecond pole opposite the first pole, and a second magnet having a thirdsurface defining a third pole and a fourth surface defining a fourthpole opposite the third pole. The second surface has a higher magneticflux density than the first surface. The third surface has a highermagnetic flux density than the fourth surface. The second magnet isspaced from the first magnet to define a first gap between the secondsurface and the third surface. Magnetic field lines of the magneticfield run from the first surface to the second surface, from the secondsurface to the third surface through the first gap, and from the thirdsurface to the fourth surface.

In another aspect, the invention provides a magnet arrangement. Themagnet arrangement includes a first magnet and a second magnet spacedfrom the first magnet to define a first gap between the first magnet andthe second magnet. The first magnet and the second magnet create amagnetic field including magnetic field lines that converge in the firstmagnet, run through the gap between the first and second magnets, anddiverge in the second magnet.

In another aspect, the invention provides a magnet. The magnet includesa first surface defining a first pole, and a second surface defining asecond pole, the second surface spaced from the first surface. Amagnetic flux increases in density from the first surface to the secondsurface, and wherein the magnet includes a substantially arcuate shapein a first cross section taken along a first plane and includes asubstantially trapezoidal shape in a second cross section taken along asecond plane substantially perpendicular to the first plane.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a magnetic refrigeration deviceaccording to one embodiment of the invention.

FIG. 2 is a perspective view of the magnetic refrigeration device shownin FIG. 1 with an outer yoke of the magnetic refrigeration deviceremoved.

FIG. 3 is a perspective view of an inner yoke of the magneticrefrigeration device of FIG. 1.

FIG. 4 is a top view of the inner yoke of FIG. 3.

FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4.

FIG. 6 is a perspective view of the outer yoke of FIG. 1.

FIG. 7 is a top view of the outer yoke of FIG. 6.

FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 7.

FIG. 9 is a perspective view of an end plate of the magneticrefrigeration device of FIG. 1.

FIG. 10 is a top view of the end plate of FIG. 9.

FIG. 11 is a cross-sectional view taken along line 11-11 in FIG. 10.

FIG. 12 is a perspective view of an outer permanent magnet of themagnetic refrigeration device of FIG. 1.

FIG. 13 is a top view of the outer permanent magnet of FIG. 12.

FIG. 14 is a front view of the outer permanent magnet of FIG. 12.

FIG. 15 is a side view of the outer permanent magnet of FIG. 12.

FIG. 16 is a perspective view of an inner permanent magnet of themagnetic refrigeration device of FIG. 1.

FIG. 17 is a front view of the inner permanent magnet of FIG. 16.

FIG. 18 is a side view of the inner permanent magnet of FIG. 16.

FIG. 19 is a top view of the inner permanent magnet of FIG. 16.

FIG. 20 is a perspective view of the magnetic refrigeration device ofFIG. 2 showing magnetic field vectors.

FIG. 21 is a cross-sectional top view of the magnetic refrigerationdevice shown in FIG. 1, taken through the middle, including arrowsindicating the magnetic field vectors.

FIG. 22 is a cross-sectional side view of the magnetic refrigerationdevice shown in FIG. 1 including the magnetic field vectors.

FIG. 23 is a plot of magnetic field strength as it varies over 360degrees at a fixed radial distance from the center of the device.

FIG. 24 is another construction of the magnetic refrigeration deviceincluding two permanent magnets.

FIG. 25 is another construction of the magnetic refrigeration deviceincluding six permanent magnets.

FIG. 26 is a perspective view of the magnetic refrigeration device shownin FIG. 25 with an outer yoke of the magnetic refrigeration deviceremoved.

FIG. 27 is another construction of the magnetic refrigeration deviceincluding twelve permanent magnets.

FIG. 28 is a top view of the individual magnets that make up the innerand outer permanent magnets.

FIG. 29 is a perspective view of the individual magnets that make up theinner and outer permanent magnets.

FIG. 30 is a perspective view of an outer permanent magnet (shown inFIG. 20) showing the direction of magnetic field vectors through it.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted,” “connected,” “supported,” and “coupled” and variationsthereof are used broadly and encompass both direct and indirectmountings, connections, supports, and couplings. Further, “connected”and “coupled” are not restricted to physical or mechanical connectionsor couplings.

FIGS. 1 and 2 illustrate a magnetic refrigeration device 10 according toone embodiment of the present invention. The magnetic refrigerationdevice 10 includes a magnet assembly 12 having an inner yoke 14, anouter yoke 16 concentrically arranged outside of the inner yoke 14, anend plate 18 coupling the inner and outer yokes 14, 16, two innerpermanent magnets 20 coupled to the inner yoke 14, and two outerpermanent magnets 22 coupled to the outer yoke 16. Two end plates 18 maybe used, but none is required. The magnetic refrigeration device 10 alsoincludes a magnetocaloric element assembly including four magnetocaloricelements 24 disposed within a gap between the inner and outer permanentmagnets 20, 22.

Best shown in FIGS. 3-5, the inner yoke 14 is a cylindrical tube havingan outer diameter B that is concentric with an inner diameter C, and aheight D. The inner yoke 14 defines an axis A. In one construction, theouter diameter B is approximately 60 mm, the inner diameter C isapproximately 40 mm, and the height D is approximately 270 mm.

Best shown in FIGS. 6-8, the outer yoke 16 is a cylindrical tube havingan outer diameter F that is concentric with an inner diameter G (aboutaxis A), and a height H. In the illustrated construction, the outerdiameter F is approximately 280 mm, the inner diameter G isapproximately 250 mm, and the height H is approximately 250 mm.

Best shown in FIGS. 9-11, the end plate 18 is a plate-like disk havingan outer diameter J that is concentric with an inner diameter K (aboutaxis A), and a thickness L. In the illustrated construction, the outerdiameter J is approximately 280 mm, the inner diameter K isapproximately 60 mm, and the thickness L is approximately 20 mm.

Best shown in FIGS. 12-15, the outer permanent magnet 22 includes aninner surface 26, an outer surface 32, and side surfaces 34. The innersurface 26 has a central surface 28 and two tapered surfaces 30 atopposite ends of the central surface 28. The height N of the outerpermanent magnet 22, the height P of the central surface 28, heights Rand S, angle V, and a width Q of the side surface 34 all generallydefine a trapezoid. In the illustrated embodiment, the trapezoid is anisosceles trapezoid. In other embodiments, the outer permanent magnet 22can take other shapes generally converging from the outer surface 32 tothe inner surface 26 (as viewed from a radial cross-section taken alonga plane that is parallel to axis A). The inner surface 26 lies at aradial distance T from the center axis A of the arc U. In theillustrated construction, the height N is approximately 250 mm, theheight P is approximately 81.56 mm, the height R is approximately 125mm, the height S is approximately 40.78 mm, angle V is approximately24.6 degrees, and width Q is approximately 38.5 mm. The trapezoid formedby these dimensions is the same for any radial cross-section of theouter permanent magnet 22 taken along a plane that is parallel to theaxis A. The inner surface 26 lies at a distance T of approximately 87.33mm from the axis A, which spans an angle of approximately 90 degrees.

As best shown in FIGS. 28 and 29, the outer permanent magnet may becomposed of a plurality of individual magnets 48 bonded together withepoxy, glue or another bonding means such that the north poles of eachof the individual magnets are adjacent. While one hundred and eightindividual magnets 48 are utilized to compose one whole magnet in theillustrated construction, fewer or more could be used in an alternateconstruction to create the same effect. In another construction, sixtyindividual magnets 48 may be utilized to compose one whole magnet. Inone construction, each individual magnet 48 effectively includes aportion of the outer surface 32 and the inner surface 26 of the outerpermanent magnet; however, it is not necessary for each and everyindividual magnet 48 to include these surfaces. In another construction,the outer permanent magnet may be constructed as a single piece havingnon-parallel magnetic field lines that converge or diverge from one poleto the other. A magnet having non-parallel magnetic field lines thatconverge or diverge is called a congruent magnet and can be constructedin any way that accomplishes this effect—including, but not limited to,the ways described above.

Best shown in FIGS. 16-19, the inner permanent magnet 20 includes aninner surface 42, an outer surface 36, and side surfaces 44. The outersurface 36 has a central surface 38 and two tapered surfaces 40 atopposite ends of the central surface 38. The height W of the outerpermanent magnet 20, the height X of the central surface 38, heights Zand AA, angle AD, and a width Y of the side surface 44 all generallydefine a trapezoid. In the illustrated embodiment, the trapezoid is anisosceles trapezoid. In other embodiments, the inner permanent magnet 20can take other shapes generally diverging from the outer surface 38 tothe inner surface 42, as viewed from a radial cross-section taken alonga plane that is parallel to the axis A (FIG. 22), and converging fromthe outer surface 38 to the inner surface 42 as viewed from a crosssection taken along a plane that is normal to the axis A (FIG. 21). Theinner surface 42 lies at a radial distance AB from the center of the arcAC. In the illustrated construction, the height W is approximately 250mm, the height X is approximately 81.56 mm, the height Z isapproximately 125 mm, the height AA is approximately 40.78 mm, angle ACis approximately 24.6 degrees, and width Y is approximately 38.5 mm. Thetrapezoid formed by these dimensions is the same for any radialcross-section of the inner permanent magnet 20 taken along a plane thatis parallel to the axis A. The inner surface 42 lies at a distance AB ofapproximately 30 mm from the center axis A. The inner surface 42 spansan angle of approximately 90 degrees.

As best shown in FIGS. 28 and 29, the inner permanent magnet is composedof a plurality of individual magnets 48 bonded together with epoxy, glueor another bonding means such that the north poles of each of theindividual magnets are adjacent and as such is called a congruentmagnet. While one hundred and eight individual magnets 48 are utilizedto compose one whole magnet in the illustrated construction, fewer ormore could be used in an alternate construction to create the sameeffect. In another construction, sixty individual magnets 48 may beutilized to compose one whole magnet. In one construction, eachindividual magnet 48 effectively includes a portion of the outer surface36 and the inner surface 42 of the inner permanent magnet; however, itis not necessary for each and every individual magnet 48 to includethese surfaces. In another construction, the inner permanent magnet maybe constructed as a single piece having non-parallel magnetic fieldlines that converge or diverge from one pole to the other. A magnethaving non-parallel magnetic field lines that converge or diverge iscalled a congruent magnet and can be constructed in any way thataccomplishes this effect—including, but not limited to, the waysdescribed above.

With reference back to FIGS. 1 and 2, the inner 14 and outer 16 yokesare made of a magnetically permeable (magnetically soft) material suchas 1010 steel or equivalent and are concentrically coupled to the endplate 18 about the axis A. The end plate is also made of a magneticallypermeable (magnetically soft) material such as 1010 steel or equivalent.The outer diameter B of the inner yoke 14 is approximately equal to andfits inside the inner diameter K of the end plate 18 so that the end ofone is flush with the end of the other. The height D of the inner yoke14 is approximately equal to the height H of the outer yoke 16 plus thethickness L of the end plate 18.

The two inner permanent magnets 20 and the two outer permanent magnets22 are high remnant flux density Br magnets such as NdFeB (NeodymiumIron Boron) N52 or any other equivalent high remnant flux density Brmagnets. The inner surfaces 42 of the inner permanent magnets 20 arecoupled to the outer diameter B of the inner yoke 14 and are spacedequidistantly from each other about the axis A. The outer surfaces 32 ofthe two outer permanent magnets 22 are coupled to the inner diameter Gof the outer yoke 16 and are spaced equidistantly from each other aboutthe axis A. Additionally, each inner permanent magnet 20 is paired withan outer permanent magnet 22 such that each pair of inner 20 and outer22 permanent magnets share the same central axis A and occupy the sameangular space with respect to that central axis A.

Shown in FIGS. 1 and 2 are the four magnetocaloric elements 24 disposedconcentrically between the inner 20 and outer 22 permanent magnets andspaced equidistantly apart from each other about the axis A. The heightof the magnetocaloric elements 24 is approximately equal to the height Xof the central surface 38 of the inner permanent magnets 20 and theheight P of the central surface 28 of the outer permanent magnets 22.The magnetocaloric elements 24 have a thickness of approximately 18 mm.Each magnetocaloric element 24 is shaped as an arc that is concentricwith the arcs of the permanent magnets 20, 22 and defines an angle thatis slightly less than the angles U, AC of the permanent magnets 20, 22.An air gap, also about 18 mm deep in the illustrated construction, islocated in between each magnetocaloric element 24. Each magnetocaloricelement 24 could be encapsulated by a thin shell made of plastic oranother material (not shown) having substantially the same shape as themagnetocaloric elements 24 shown in the figures, wherein themagnetocaloric element 24 is disposed inside the thin shell in the formof a powder or beads.

Although not illustrated, it is understood by those of ordinary skill inthe art that each magnetocaloric element 24 could include at least oneinlet, at least one outlet, at least one pump and at least one valve anda system of pipes (not shown) configured to allow a fluid to flowthrough and provide heat transfer between the magnetocaloric elements 24and hot and cold heat exchangers. The hot heat exchanger can be used torelease heat into the atmosphere and the cold heat exchanger can be usedto cool a space, such as a refrigerator. The present magnet assembly 12design is advantageous because it provides ample space in which suchfeatures can be disposed.

The inner yoke 14 is coupled to a rotating device, such as a motor (notshown), so that the entire magnet assembly 12 rotates together as onepiece around the magnetocaloric elements 24 at a speed betweenapproximately 0.1 and 10 rotations/second. As the motor rotates, theinner yoke 14 and the outer yoke 16 share a common angular velocity.During rotation about the axis A, there is no relative movement betweenthe inner and outer permanent magnets 20, 22. Alternatively, themagnetocaloric elements 24 could be configured to rotate and the magnetassembly 12 could be configured to remain stationary.

FIG. 20, which illustrates the concept of congruent magnets, shows theflow direction of the magnetic field vectors 46 through the inner andouter permanent magnets 20, 22 in a view similar to that of FIG. 2. Eachindividual magnet 48 produces magnetic field vectors that travelparallel to each other. However, the permanent magnets 20, 22 as a wholeare congruent magnets, which have a converging or diverging magneticfield that follows the convergent and divergent shape of the magnets asa whole. FIG. 20 shows that the magnetic field vectors 46 of the presentinvention are neither parallel nor do they travel in only one direction;rather, the magnetic field vectors 46 are shown in three dimensions tochange direction continuously from one side of the magnet to the other.As a result, the strength of the magnetic field increases as the vectors46 converge and become increasingly concentrated within the space.

The shape and construction of the magnets 20, 22 of the presentinvention, with the convergent portions being adjacent to themagnetocaloric elements 24, concentrates (and thus strengthens) themagnetic field 46 through the magnetocaloric elements 24 disposedbetween the magnets 20, 22. These vectors 46 are also shown in FIG. 21,which is a cross-sectional top view that cuts through the middle of themagnetic refrigeration device 10 at a height of about 125 mm from aninner surface of the end plate 18, along with the magnetic fieldstrength measured in Tesla.

As shown in FIGS. 21 and 22, the arrangement and construction of theinner and outer permanent magnets 20, 22 and the inner and outer yokes14, 16 produces a significant magnetic field, as high as approximately 2Tesla in parts of the outer yoke 16, parts of the inner permanentmagnets 20 and parts of the magnetocaloric elements 24 or gaps adjacentto the inner permanent magnets 20.

The outer permanent magnet 22 converges from the outer surface 32 to itsinner surface 26 by the radial side surfaces 34 and the tapered surfaces30. The surface area of the outer surface 32 is greater than the surfacearea of the inner surface 26. Accordingly, the magnetic field density inthe outer permanent magnet 22 also converges, or increases in density,from the larger outer surface 32 to the smaller inner surface 26 whenthe magnetic field lines run from the outer surface 32 to the innersurface 26. Conversely, when the magnetic field lines run from the innersurface 26 to the outer surface 32, the magnetic field density in theouter permanent magnet 22 diverges, or decreases in density, from theinner surface 26 to the outer surface 32. The direction of the fieldlines depends on which of the inner and outer surfaces 26, 32 is thenorth pole and which is the south pole.

The inner permanent magnet 20 converges in shape from the outer surface36 to the inner surface 42 by the radial side surfaces 44, as viewed inFIG. 21. However, when viewed from a side cross section as in FIG. 22,the inner permanent magnet 20 diverges in shape from the outer surface36 to the inner surface 42 by the tapered surfaces 40. The surface areaof the inner surface 42 is greater than the surface area of the outersurface 36. Accordingly, the magnetic field density in the innerpermanent magnet 20 diverges, or decreases in density, from the smallerouter surface 36 to the larger inner surface 42 when the magnetic fieldlines run from the outer surface 36 to the inner surface 42. Conversely,when the magnetic field lines run from the inner surface 42 to the outersurface 36, the magnetic field density in the inner permanent magnet 20converges, or increases in density, from the inner surface 42 to theouter surface 36. The direction of the field lines depends on which ofthe inner and outer surfaces 36, 42 is the north pole and which is thesouth pole.

The respective side surfaces 34, 44 of the inner and outer permanentmagnets 20, 22 are substantially aligned. The inner and outer surfaces42, 26 of the inner and outer magnets 20, 22 are all concentricallypositioned about the axis A. By way of this arrangement, the magneticfield passes through a first pair of inner and outer permanent magnets20, 22 generally in a first direction toward the axis A, passes throughthe inner yoke 14 and axis A, and passes through the second oppositepair of inner and outer permanent magnets 20, 22 generally in the firstdirection, but away from the axis A. This general first direction of themagnetic field defines north and south poles relative to the entiremagnetic assembly 12.

FIG. 22 shows a side cross-sectional view of the magnetic field vectors46 passing through the magnetic refrigeration device 10. In thiscross-sectional view, the inner and outer permanent magnets of each pairof permanent magnets are substantially mirror images of each other aboutan axis extending vertically through the center of the magnetocaloricelement 24. However, the south pole and north pole of each permanentmagnet 20, 22 alternates in the direction of the magnetic field vectors46, and is therefore not symmetrical.

Shown in FIG. 23 is a plot of magnetic field strength as it varies over360 degrees at a fixed radial distance from the center axis A of thedevice 10, where this radial distance terminates in the middle of amagnetocaloric element 24 (or air gap), starting at one end of amagnetocaloric element 24 that is disposed between the inner and outerpermanent magnets 20, 22, and moving first in a direction through themagnetocaloric element 24. The x-axis of the plot is the circumferentiallength of this radial distance in mm, but can also be interpreted asstarting at 0 degrees (corresponding to 0 mm) and ending at 360 degrees(corresponding to 487 mm). The plot shows two peaks and two troughs,each being substantially flat. The peaks, approximately 1.46 Tesla,correspond to the magnetic field strength in the center of themagnetocaloric elements 24 that are disposed between the permanentmagnets 20 and 22. The troughs, approximately zero Tesla, correspond tothe magnetic field strength in the magnetocaloric elements 24 notdisposed between the inner outer permanent magnets 20, 22. The flatnessof the peaks and troughs is significant because it shows that thismagnetic refrigeration device configuration allows a high magnetic fieldstrength to be maintained throughout the circumferential length of themagnetocaloric elements 24 disposed between the permanent magnets 20,22, and that a low magnetic field strength is maintained throughout thecircumferential length of the magnetocaloric elements 4 not disposedbetween the permanent magnets 20, 22. This feature of the invention isparticularly desirable in magnetic refrigeration devices becausemagnetocaloric materials change temperature with changing magneticfields, so the more uniformly distributed the magnetic field isthroughout the magnetocaloric element, the more efficient the magneticrefrigeration device will be.

Another feature of this invention that improves the efficiency of themagnetic refrigeration device 10 is the configuration of the outer yoke16 and the material selected for it. Magnetically permeable materialsprovide a path through which the lines of a magnetic field easilyfollow. FIG. 21 confirms this by showing that as the magnetic fieldlines exit the north pole of the outer permanent magnet 22, the magneticfield lines then travel almost entirely through the outer yoke 16 (at astrength of approximately 2 Tesla) towards the south pole of the otherouter permanent magnet 22. The magnetic field lines shown escaping theouter yoke 16 have a very low strength of approximately 0.2 Tesla orless. Therefore, there is very little magnetic leakage with this design,which makes it more efficient.

Advantages of the congruent magnet construction include the fact thatless magnetic material is required to produce a stronger magnetic field,i.e., the ratio of total magnet volume to magnetic field workspacevolume (for example, the volume of the two magnetocaloric elements 24disposed between the magnets 20, 22) is lower than in previousdesigns—preferably a ratio of less than 25. It is also lower than anon-congruent magnet construction having the same overall shape, i.e.,if the inner and outer magnets had parallel magnetic field lines and thesame shape and dimensions as the congruent magnets 20, 22, the congruentmagnet arrangement would have a lower ratio. This is another way ofsaying that less magnet material is needed to create a certain magneticfield strength in a workspace when the magnets are congruent magnets, asdescribed by the present invention.

Additionally, a magnetic refrigeration device having any even number ofpermanent magnets in a similar configuration could be used. For example,FIG. 24 shows a second construction of a magnetic refrigeration devicehaving two permanent magnets (one inner and one outer). This secondconstruction could be used with two magnetocaloric elements. Figure 25shows a third construction of a magnetic refrigeration device having sixpermanent magnets (three inner and three outer) and 6 magnetocaloricelements. FIG. 26 shows a second view of the third construction with theouter yoke hidden from view. FIG. 27 shows a fourth construction of amagnetic refrigeration device having 12 permanent magnets (six inner andsix outer) and 12 magnetocaloric elements.

Furthermore, the permanent magnet configurations of the presentinvention need not be limited to applications in magnetic refrigeration.Such magnet configurations may also be used with data storage devicessuch as floppy disks, scan disks, and flash drives, for example, toerase data from these devices or manipulate the data in other ways.

1. A magnet arrangement for creating a magnetic field, comprising: afirst magnet having a first surface defining a first pole and a secondsurface defining a second pole opposite the first pole, wherein thesecond surface has a higher magnetic flux density than the firstsurface; a second magnet having a third surface defining a third poleand a fourth surface defining a fourth pole opposite the third pole,wherein the third surface has a higher magnetic flux density than thefourth surface, wherein the second magnet is spaced from the firstmagnet to define a first gap between the second surface and the thirdsurface, and wherein magnetic field lines of the magnetic field run fromthe first surface to the second surface, from the second surface to thethird surface through the first gap, and from the third surface to thefourth surface.
 2. The magnet arrangement of claim 1, wherein themagnetic flux density in the gap is larger than the magnetic fluxdensity of the first surface.
 3. The magnet arrangement of claim 1,further comprising: a third magnet having a fifth surface defining afifth pole and a sixth surface defining a sixth pole opposite the fifthpole, wherein the sixth surface has a higher magnetic flux density thanthe fifth surface, and wherein the magnetic field lines run from thefourth surface to the fifth surface and from the fifth surface to thesixth surface; a fourth magnet having a seventh surface defining aseventh pole and an eighth surface defining a eighth pole opposite theseventh pole, wherein the seventh surface has a higher magnetic fluxdensity than the eighth surface, wherein the fourth magnet is spacedfrom the third magnet to define a second gap between the sixth surfaceand the seventh surface, and wherein the magnetic field lines run fromthe sixth surface to the seventh surface through the second gap, andfrom the seventh surface to the eighth surface.
 4. The magnetarrangement of claim 3, wherein the magnetic flux density in the secondgap is larger than the magnetic flux density of the eighth surface. 5.The magnet arrangement of claim 3, further comprising a firstmagnetically permeable material disposed between the second magnet andthe third magnet to create a path for the magnetic field lines to runfrom the fourth surface to the fifth surface through the firstmagnetically permeable material.
 6. The magnet arrangement of claim 5,further comprising a second magnetically permeable material disposedadjacent the first surface and the eighth surface to create a path forthe magnetic field lines to run from the first surface to the eighthsurface through the second magnetically permeable material.
 7. Themagnet arrangement of claim 1, wherein the second surface has lesssurface area than the first surface.
 8. The magnet arrangement of claim1, further comprising a magnetocaloric material disposed in the firstgap.
 9. The magnet arrangement of claim 1, wherein the first magnet isformed of a plurality of magnet segments, wherein at least one of themagnet segments includes a portion of the first surface and a portion ofthe second surface, wherein each of the magnet segments includesparallel magnetic field lines, and wherein the first magnet includesnon-parallel magnetic field lines.
 10. The magnet arrangement of claim1, wherein the second surface is arcuate and the third surface isarcuate, and wherein the second surface and the third surface share acommon arc center.
 11. A magnet arrangement, comprising: a first magnet;and a second magnet spaced from the first magnet to define a first gapbetween the first magnet and the second magnet; wherein the first magnetand the second magnet create a magnetic field including magnetic fieldlines that converge in the first magnet, run through the gap between thefirst and second magnets, and diverge in the second magnet.
 12. Themagnet arrangement of claim 11, further comprising: a third magnet; anda fourth magnet spaced from the third magnet to define a second gapbetween the third magnet and the fourth magnet; wherein the third magnetand the fourth magnet contribute to the magnetic field includingmagnetic field lines that run from the second magnet to the thirdmagnet, converge in the third magnet, and diverge in the fourth magnet.13. The magnet arrangement of claim 12, further comprisingmagnetocaloric material disposed in the first gap and in the second gap.14. The magnet arrangement of claim 11, further comprisingmagnetocaloric material disposed in the first gap.
 15. The magnetarrangement of claim 14, wherein one of the magnetocaloric material andthe first and second magnet is configured to move relative to the otherone of the magnetocaloric material and the first and second magnet. 16.The magnet arrangement of claim 14, wherein the surface areas of thepoles of the first magnet decrease in the direction of the magneticfield lines and the surface areas of the poles of the second magnetincrease in the direction of the magnetic field lines.
 17. A magnet,comprising: a first surface defining a first pole; a second surfacedefining a second pole, the second surface spaced from the firstsurface; wherein a magnetic flux increases in density from the firstsurface to the second surface, and wherein the magnet includes asubstantially arcuate shape in a first cross section taken along a firstplane and includes a substantially trapezoidal shape in a second crosssection taken along a second plane substantially perpendicular to thefirst plane.
 18. The magnet of claim 17, wherein the first surface andthe second surface are substantially arcuate.
 19. The magnet of claim17, wherein the first surface has a greater surface area than the secondsurface.
 20. The magnet of claim 17, further comprising a magnetic fieldwithin the magnet including non-parallel magnetic field lines betweenthe first and second surfaces.